Automatic tool change

ABSTRACT

A method for automatically removing a tool from a rotational shank shaft of a three-dimensional robot by indexing the shank shaft, disposing a tool tightening member provided in connection with the indexed shank shaft to a releasing device by movement of the robot, the releasing device being disposed during this operation inside the movement range of the robot; using the releasing device to release the tool; and removing the tool from the shank shaft of the robot by a movement of the robot.

The present invention relates to a method for an automatic tool changeand an apparatus carrying Out the method. More precisely, the presentinvention relates to a method and an apparatus used in connection withan automatic change of rotating tools of robots or similar devices.

It is prior known to use various rotating tools in machining operationsperformed by a robot, the operations being such as drilling, grinding orburring. The arm of said robot is provided with drive means, e.g. with apneumatically or hydraulically operated motor, said drive means beingprovided with a tool secured to a rotatable axis or shaft of said motor.It has been known to use commercially available tool holding systems,e.g. quick-release taper shanks, which are prior known by the manskilled in the art for the clamping of said tool to said rotatable axis.However, in spite of the all-round operations of a robot, the toolchange has been in general performed manually. This is due to severalreasons, among others, since the robots generally in use are not able tocarry and accurately move particularly heavy loads in the end of the armthereof and therefore the rotating devices used are made as simple andlight-weighted as possible. Thus the automatically operating toolholding and tightening devices used in normal machine tools, such aslathes, are too big in size, complicated and heavy to be used in therobot applications. Furthermore, said rotating tools require one furtheraxis of movement, i.e. rotation, which cannot be provided to the end ofa robot arm in the same manner as it is arranged in said machine tools,since the free three-dimensional movements of said robot prevent theproviding of the rotating torque by similar mechanical means as thoseused, for example, in said lathes for providing the rotational movement.Adding one further axis of movement and a programmed indexing of anangular position of said axis to the control means of a robot isdifficult and in use the programming work would be too difficult andtime-consuming to be economically profitable.

DE-patent 3208621 discloses one solution for the automatic clamping of atool. The apparatus comprises a clamping nut provided about the toolholder provided in the axis of said robot. Said tool, provided with aparallel shank is disposed through said nut and said nut is tightened bya cooperation of a special toothed rack which is driven by a workcylinder and a support means driven by a further work cylinder. Asignificant disadvantage of the arrangement disclosed in saidpublication is, however, that only tools with parallel shanks can beused, since the angular position (i.e. the rotational position) of thepart of said robot receiving said tool is not known. This results in aninsufficient ability of transferring the power required in modernmachining appliances. Furthermore, only tools having equal shankdiameters can be used in the arrangement disclosed in saidDE-publication.

The use of an arrangement according to said DE-publication is alsodifficult because of the relatively big size of said tightening nut,which makes the working of the robot more difficult. Furthermore, thetotal equipment disclosed is very space consuming in the movement rangeof the robot. The arrangement is also very complicated and it comprisesnumerous parts which require very precise manufacturing and which partsare easily blocked-up by the chips generated during the machiningprocess and the dirt present in work shops or similar environments. Thiseasily results in the jamming of said parts. Furthermore, it has beenfound difficult to control the correct tightening force of said clampingnut of said tool by the device disclosed in said publication andcomprising a pneumatic or hydraulic work cylinder, In many cases thereis also a significant disadvantage in that the exact rotational positionof the tool is not known when initiating the machining process or inthat the angular position of said tool cannot be automatically indexedto a predetermined position.

Thus, the rotating tools used in robot appliances are mainly changedmanually. This has resulted in a partial loss of the advantages whichare the object of the machine automation. In other words, because of thefrequent tool changes the robot requires an operator who manuallychanges said tools.

Therefore it is an object of the present invention to overcome saiddisadvantages of the prior art solutions and to provide a totally newsolution for the automatic tool change of a robot or the like.

Furthermore, an object of the present invention is to provide anautomatic tool changing system, in which said tool change utilizes themotions of said robot and in which system the change is performed in aquick, simple and reliable manner.

It is a further object of the present invention to provide a toolchanging system in which the tool holder for the rotating tool can beany of the generally commercially available toolholders normally used inmachining tools, such as lathes.

A further object of the present invention is to provide a tool changingsystem in which said tools can be stored in a simple tool rack, fromwhich a single tool can be picked up by the robot and to which said toolcan be replaced after use.

The invention is based on the idea that by adjusting an angular positionof a rotatable axis i.e. by indexing said rotatable axis and atightening member of a tool clamping means provided in said axis byspecific indexing means to a predetermined position said tighteningmember can then be precisely disposed by a motion of said robot withinthe reach of a separately disposed tightening and/or releasing device,said suitably device(s) preferably being externally provided and capableof tightening and releasing said tightening member, e.g. a tighteningscrew.

More precisely, the method for an automatic tool change according to thepresent invention is mainly characterized by what is disclosed inappended claims 1 to 6 and especially by the characterizing portions ofclaims 1 and 2. The system for an automatic tool change according to thepresent invention is mainly characterized by what is disclosed inappended claims 7 to 15 and especially by the characterizing portion ofclaim 7.

According to a preferred embodiment of the present invention an end of arobot arm is provided with a drive device unit assembled in a suitablemanner to said arm, said drive unit being adapted to provide at leastsome turning, reciprocating or rotating movement to the shaft relativeto the center axis thereof, said shaft being provided with a toolreceiving tool clamping device. Said drive means may be of any suitabletype by which the appropriate motion, in most cases a rotationalmovement, of said shaft can be provided. Thus it may be a hydraulic,pneumatic or electric motor or a similar device, which is assembled in asuitable manner to said drive device unit. Furthermore, said drivedevice may preferably be rotatable in both directions and the speed andthe torque of rotation can preferably be adjusted by suitable means. Thetool clamping means or tool holder comprises a tool receiving portion,which includes clamping means for the tightening of the received toolfirmly to its location in said toolholder.

Said clamping means comprise means inside said holder for providing atight hold of said tool and a tightening member operated from theoutside of said holder, said member being e.g. a tightening screw, aquick-release adapter or the like part of a hydraulic or pneumatictightening system, said member providing the clamping moment or force bywhich said means disposed inside said holder lock said tool to itsposition. The preferred by screw operated or hydraulic or pneumatictoolholders are commercially available and, thus, the construction ofthese is not described in more detail in this connection.

The system according to the present invention further includes releasingand/or tightening means disposed within the movement range of said robotor the like apparatus capable of performing three-dimensional movements.Said releasing and/or tightening means are preferably movable such thatthey can be moved inside said movement range of said robot when the toolchange is about to be initiated and then be moved outside said rangeafter said tool change is completed. The releasing and/or tighteningmeans may be, for example, a hydraulic, pneumatic or electric device orany another suitable device which can provide a motion, change ofpressure or another function that releases and/or tightens saidtightening member. In one preferred embodiment the torque of therotational tightening movement is controllable during the releasingand/or tightening movement.

According to one embodiment of the present invention the releasingand/or tightening means is a solidly assembled and suitably formed toolor wrench by which the tightening member is released and tightened suchthat the clamping effect caused by said tightening member is affected bythe movement of said robot's wrist or arm. This structure is preferredin cases in which said releasing and/or tightening movement of saidtightening member is essentially short such that the movement of saidrobot arm is sufficient for totally releasing and tightening saidtightening member. This kind of stationary tool is also preferred whenthe turning and rotating of the tightening members is performed byreleasing and/or tightening means whose torque is not adjustable. Inthis case the releasing and tightening steps of the torque of saidtightening member can be performed more carefully by the movement ofsaid robot, thus avoiding breakage of the tool clamping devices in saidtoolholder, after which tightening members having quite a long range ofmovement can be rotated by similar non-adjustable means as mentionedabove.

According to one preferred embodiment of the present invention ahydraulically or pneumatically operated tool holder structure is used.According to the present invention a tool clamping member is, afterindexing of the rotating axis thereof, brought by a movement of a robotor the like to a releasing and/or tightening means, which is providedwith a fast coupling suitable to cooperate with the fluid coupling ofsaid tool clamping member. By decreasing/increasing the fluid pressurethrough said coupling, said tool can be released/locked to its position.

In a preferred embodiment according to the present invention saidtightening member is brought into a predetermined position by indexingthe shank axis by means of an indexing apparatus included in the toolchanging system. Said apparatus preferably comprises means disposed inthe periphery of said axis for receiving a protruding member disposedadjacent to said axis and arranged to be moved towards and away fromsaid axis, by which means the rotational or turning movement of saidaxis can be stopped into a predetermined angular position. Furthermore,it is preferable to provide several stopping members closely adjacent toeach other on said axis and to arrange said protruding member to bemovable also in the axial direction of said axis, whereby more stoppositions are provided.

According to one preferred embodiment of the present invention thestopping means on the periphery of the axis is formed by providing saidaxis with a discontinuous groove about the periphery thereof, Theprotruding member has a width that is less than the width of said grooveand thus it can penetrate into said groove. The bottom of said groove isprovided with at least one discontinuity, which is preferably such thatthe radius of the top of said discontinuity is greater than the radiusof the bottom of said groove and not greater than equal to the radius ofsaid axis.

According to an another preferred embodiment of the present invention acircular sleeve is arranged on the axis, said sleeve being provided withat least one bulge or stoppage forming the stopping member for saidprotruding member. By the use of such a sleeve a further machining ofsaid shank axis is avoided.

According to a third embodiment of the present invention the indexingmeans is arranged by providing a pin-like protruding member and a hole,notch or slot provided on said axis, into which said protruding memberpenetrates towards the center of said axis with the assistance of alight biasing force provided, for example, by a spring or by pressurizedair.

According to a further preferred embodiment the indexing means isprovided by a structure in which an angularity sensor or pick-offdetects the angular position of said axis. Said angularity sensornormally comprises means disposed on said axis for indicating theangular position and means disposed close to said axis for detectingsaid angular position. Such sensors are prior known and they may be,among others, optical, inductive or capacitive sensors or pick-offs.During the indexing, after detecting of said angular position said axiscan be stopped and thereafter be held in the predetermined position in anumber of different ways, for example by a mechanical brake whichsettles about the periphery of said axis and is operatively connected tosaid angularity sensor, or by an electrical field or the likeoperatively connected to said angularity sensor. An advantage of thiskind of indexing is that the axis can be steplessly positioned in anypossible angular position according to the output information of theangular position by said sensor.

According to a preferred embodiment of the method according to thepresent invention a tool releasing work cycle is initiated by indexing ashank axis, i.e. by bringing said axis precisely to a predeterminedangular position. During the indexing said axis is rotated with a lowtorque by a drive means of said axis or an external device. For example,it is possible to utilize the movement of a robot and a suitablesurface, for example a planar or curved surface, whereby the relativemovement and the friction between said axis and said surface providesthe rotation of said axis. After indexing, the toolholder means is movedby the movement of said robot to a releasing means disposed inside themovement range of said robot. A tightening member provided in saidtoolholder means is suitably fitted by said robot in said releasingmeans, whereafter the releasing operation of said releasing means isinitiated and the clamping caused by said tightening member is looseneduntil said tool is released. After this the released tool stillremaining in said holder is transferred by the movement of said robot toa tool rack. Said tool is prevented from dropping out from said holdersince said toolholder is preferably swung by the wrist of said robot tosuch a position that said tool remains in the opening of said holder inconsequence of gravity during the releasing operation and during thetransfer to said tool rack. During the transfer the tool can also beheld in other suitable arrangements, such as a light retaining force,which the tool rack is arranged to release.

According to a preferred embodiment the releasing of the clamping ofsaid tool occurs in the tool rack, which can be provided with, forexample, means which grip said tool and which after the releasing ofsaid tool take said tool to its predetermined place in said rack, oralternatively with means which are arranged to release said clamping ofsaid tool after said tool is placed by said robot in its predeterminedplace of storage.

According to one embodiment of the present invention the releasing ofthe tool is performed in two stages such that in the first stage theclamping torque is released by disposing the tightening member in asuitable fixed mounted tool and the tightening member is released by amovement of the robot's arm or wrist and in the second stage saidtightening member, which is no longer under clamping torque but whichstill holds said tool is released by a suitable device, for example by arotatable pneumatically operating means or other suitable means.

Consequently, according to a preferred embodiment of the method of thepresent invention the positioning of a tool includes the followingsteps: indexing of the axis as described above, retrieving said toolfrom a tool rack by a movement of said robot, bringing said tool in thetoolholder and the tightening member into the reach of the tighteningmeans, bringing said tightening means and tightening member into anoperational relationship, clamping said tool by said tightening meansand releasing the indexing apparatus.

The automatic tool chancing system according to the present invention isespecially well suited to being used in machine automation appliances,In which rotating or turning tools are required and in which the toolholding system has to be light and simple, but also precise andreliable. Such systems, are for example various manipulators, chancingsystems of rotating tools of machine tools and the like, in addition tothe above described robot appliances.

In the following the present invention and the objects and advantagesthereof will be described by way of an example with reference to theannexed drawings, in which similar reference characters throughout thevarious figures refer to similar features. It should be understood thatthe following description of an example of the invention is not meant tolimit the invention to the specific forms presented in this connectionbut rather the present invention is meant to cover all modifications,similarities and alternatives which are included in the spirit and scopeof the present invention, as defined by the appended claims.

FIG. 1 is a schematic general view of a robot unit utilizing a toolchanging system according to the present invention.

FIG. 2 is a view partially in section of a drive device unit disposed atthe end of the robot arm.

FIG. 3 is a more detailed view of a shank axis of the drive device unitand of one embodiment of an indexing apparatus.

FIG. 4 is a presentation of one tightening system for the tool clampingand of one tool suitable for the tightening thereof.

FIGS. 5a, 5b, 5c, 5d and 5e disclose indexing means according to thepresent invention.

More particularly, a preferred embodiment of an automatic tool changingsystem is disclosed in the form of a principle presentation in FIG. 1.FIG. 1 discloses a robot arm 10, which is provided with a drive unit 20at one end thereof. Said drive unit comprises a drive device which isarranged to rotate a shank axis 22. Said drive device is of a suitabletype such as a pneumatic, hydraulic or electric motor. For theaccommodation of a tool 26 a suitable toolholder 24 is assembled to saidshank axis 22. A tool tightening member 28 is disposed in said shankaxis, said member being in this connection shown as a screw. Inside themovement range of said robot are disposed a releasing device 30 andtightening device 32 of the tightening member 28 and a fixed releasingtool 31 connected to said releasing device. Devices 30 and 32 and saidfixed tool 31 are provided with a tightening tool 34, which is adaptedto be compatible with said tightening member. It should be noted thatthe releasing and tightening device of the tightening member may also bedesigned as one single device, which is capable of rotating in bothdirections of rotation, and that said devices in FIG. 1 are shown asseparate ones for the purposes of clarity only. Said releasing andtightening devices 30, 32 are preferably arranged to be pneumatically,hydraulically or electrically driven. Said releasing and tighteningdevices are also preferably operationally connected to a control systemof said robot or the like. Furthermore, said releasing and tighteningdevices are preferably arranged to be movable into said range ofmovement of said robot and away from said range of movement alongguideways 35. FIG. 1 discloses also a rack 60 for said tools 26.

FIG. 2 is a view partially in section of the drive unit 20, which has ajoint surface 21 for the assembly to said robot or the like. A drivedevice (not shown) is arranged to rotate said axis 22, which is mountedwith bearings 25 to the frame of said drive unit. Said tool clampingtoolholder 24 is mounted at the other end of said axis. In theembodiment shown in FIG. 2 the clamping of said tool is arranged to beoperated by hydraulic or pneumatic fluid and thus a quick-releaseadapter 36 provided in said axis 22 and a cooperating fluid connectioncounterpart 37 are also disclosed.

Said axis 22 is further provided with an indexing apparatus, generallydesigned at 40, which in the presented embodiment suitably comprises aprotruding member 42 and a discontinuous groove 44 for receiving saidprotruding member.

FIG. 3 discloses in more detail one embodiment of said shank axis 22 andsaid tool clamping means 24 provided thereon as well as said indexingmeans 40. In this embodiment said indexing means 40 comprises a sleeve46 mounted onto said axis, said sleeve being provided with shoulders 47and 47' for receiving said protruding member. A preferred drive meansfor said protruding member 42 is also disclosed in this Figure, saidmeans being arranged to move said protruding member towards said axisand away therefrom and said means being suitably operationally connectedto a control system of a robot or the like.

FIG. 4 discloses, by way of an example only, a radial directionsectional view of an axis 22 of a prior known toolholder previously usedonly in connection with machine tool applications and a fixedly mountedtightening and releasing tool 31 according to the present invention.FIG. 4 indicates how, by rotating the tightening screw 28 with said toolin the way shown by a two-headed arrow 58 by a movement of robot'swrist, the clamping balls lock said tool 26 in its place in said holder,and correspondingly, by loosening said tightening screw said tool isreleased.

FIG. 5a is a sectional view of the axis along line A--A of FIG. 2 andshows one embodiment of the indexing apparatus 40. Around the peripheryof said axis 22 is provided a discontinuous groove 44, said groovehaving a discontinuity 45. The Figure also shows a protruding member 42,which is arranged to move towards said axis 22 and away therefrom. Whensaid robot or the like is working said protruding member is disposed inthe farthest position thereof relative to said axis 22 and during theindexing operation it is moved into said discontinuous groove 44 of saidaxis, as shown by the broken line in FIG. 5a. Several adjacent groovesmay be provided or one groove may include several discontinuities.

FIG. 5b is a sectional view of the axis along line B--B of FIG. 3 andshows another embodiment of the indexing apparatus. In this embodiment asleeve 46 is mounted about the periphery of said axis 22, which sleeveis provided with the receiving shoulders 47, 4' for the protrudingmember.

FIG. 5c discloses as a partially sectioned view a further embodiment ofthe indexing apparatus, in which the member on said axis for receivingan indexing pin 49 is formed by a bore 48 provided into said axis. Saidindexing pin 49 is suitably shaped at the end facing said axis and isslightly biased by a spring 51. Alternatively, said biasing may beprovided by, for example, a small pneumatic cylinder. FIG. 5c alsodiscloses a second and third bore 48', 48", which are disposed on theperiphery of said axis and spaced from each other in the longitudinaldirection of said axis to allow several stop positions.

FIG. 5d discloses an angularity sensor or pick-off comprising an axisposition indicator 52 mounted on said axis and a detector 53operationally connected therewith. A suitable angularity sensor ispreferably an optical, inductive or capacitive sensor. This Figureshowing one embodiment of the indexing apparatus further discloses anelectric magnet 54 operationally connected to said angularity sensor andarranged to stop said axis 22 in a predetermined angular position.

FIG. 5e is similar to that shown in FIG. 5d, but in this embodiment theelectric brake is replaced by a mechanical friction brake 55.

When using the automatic tool changing device according to the presentinvention the tool change cycle is initiated when a drive unit 20provided at one end of a robot arm 10 initiates the indexing step of ashank axis 22. Said shank axis of said drive unit 20 is rotated at a lowspeed by drive means of said axis or alternatively by suitable externalmeans and an indexing apparatus 40 is activated. A protruding element 42according to FIG. 5a, 5b or 5c moves towards said axis and causes incooperation with a receiving member 45, 47 or 48 a stopping of therotational movement of said axis. Said protruding member is held in itsposition close to said axis abutting said receiving member and due tothe torque of said axis said axis is held in this position during theperiod of tool change.

The alternative indexing apparatus disclosed in FIGS. 5d and 5e operatessuch that an angularity sensor detects the angular position of the axisand a means operationally connected to said angularity sensor andproviding an electromagnetic field or a mechanical brake or any othersuitable means stops the rotation of said axis 22 in a predeterminedangular position and holds said axis in this position during thetoolchange process. In this alternative, the rotating torque of saidaxis may be removed immediately after the stopping means have performedsaid stopping.

Since the angular position of said axis stopped as described above isnow known, said axis is indexed. Said indexed axis, comprising aclamping means tightening member, such as a screw, the position of whichis thus now known, is then brought by a movement of an arm or wrist ofsaid robot to a releasing means of said tool tightening member and saidtightening member is fitted to a tool or wrench of said releasing meanscompatible with said tightening member or to any other suitable meansfor this purpose. After this, said releasing means is activated and itrotates or twists said tightening member open and thus releases saidtool. In one alternative embodiment the internal fluid pressure of atool holding means is changed whereby said tool is released. Theposition of said toolholder is preferably set such that said releasedtool cannot drop out. It is also possible to use various light holdingor biasing means which prevent said tool from sliding out from saidholder but from which the removing of said tool to a tool rack can beeasily performed.

According to one preferred embodiment the clamping of said tool isreleased only after said tool is in said tool rack, which rack includessuitable means for releasing said tool and for transferring said tool toa predetermined position thereof or means for releasing said tool onlyafter said tool is already brought into its final place of storage.

Alternatively, in some cases the clamping of said tool is partiallyreleased beforehand, i.e. the clamping force or torque is removed beforethe tightening member is placed into the device rotating said tighteningmember totally open. In this case said tightening member is brought intocooperation with a tool or wrench which is fixedly assembled and whichfits to said tightening member and said clamping force is then opened,preferably by a movement of the robot arm or wrist. Then said openedtightening member still retaining said tool is brought to a rotatablereleasing device and is rotated totally open.

The above described embodiment is preferable when using simple releasingdevices, in which the torque cannot be adjusted. In such a case it ispossible to choose a releasing and tightening device with has so lowtorque that it cannot break the clamping elements of the toolholder, butis capable, however, of rotating a loosened tightening member, such as atightening screw. The loosening of said clamping force, which requiresmore power, may be performed by said robot having more easilycontrollable movements.

Furthermore, only a sole combination of a robot and a fixedly assembledopening tool is needed when the clamping system of the toolholder usedis such that the releasing/tightening of a tightening member requiresless than one full turn to be rotated for said releasing/tightening ofsaid tightening member.

The released tool is preferably transferred by the robot to the toolrack and a new predetermined tool may be picked up at the same time,When the operation is initiated, for example in the morning after theequipments have been cut off, the tool adjustment operation is initiatedwith an indexing of the shank axis. In case the adjustment operation ofa new tool follows immediately after the removal of the previously usedtool, the indexing of said axis is still on and thus needs not to berepeated. The tightening member of the tool holding means for saidpicked tool is transferred by the movement of said robot to a tighteningmeans, which may be said releasing means, but which is now rotated in adifferent direction. Said tightening member is clamp ed and saidindexing is released, and said tool is ready for use.

Thus the present invention provides an apparatus and method, by which atool change of a robot or the like can be per formed automatically. Saidapparatus is simple in construction but reliable and precise inoperation.

It should be noted that the foregoing examples of some embodiments ofthe present invention do not restrict the scope of protection defined inthe appended claims. With the aid of the above description and theappended drawings it is clear to those skilled in the art to use, forexample, a tool tightening member comprising at least one V-shaped meansbeing fitted to cooperate with the toolholder or the axis to provide aclamping of the tool. It is also clear to those skilled in the art thatthe shank axis indexing apparatus may be placed in any position fromwhich the above described effect of indexing the angular position of theaxis can be provided.

I claim:
 1. A method for automatically clamping a tool to a rotationalshank shaft of a robot or similar apparatus performing three dimensionalmovements, the method comprising the steps of:indexing said shank shaftof the robot or similar apparatus to an angular position; accommodatingsaid tool into a toolholder provided in said indexed shank shaft of therobot or similar apparatus; disposing a tool tightening member providedin connection with said indexed shank shaft in a drive means of saidtool tightening member by a movement of said robot or similar apparatusperforming three dimensional movements, said drive means being disposedat least during said tool accommodating operation inside the movementrange of said robot or similar apparatus; and tightening said tighteningmember by said drive means of said tool tightening member to apredetermined tightness for clamping of said tool into said toolholderprovided in said indexed shank shaft of the robot or similar apparatus.2. A method as set forth in claim 1, wherein said indexing of said shankshaft comprises:moving an indexing means towards said shaft to apredetermined distance from said shaft; rotating said shank shaft with alow torque and such that said indexing means reaches a counterpartthereof provided in said shank shaft, whereby the rotation of said shankshaft stops and the angular position of said shank shaft is maintainedby a cooperation of said indexing means and said counterpart thereof. 3.A method as set forth in claim 2, wherein the rotation of said shankshaft during the indexing is provided by:moving a part of said shankshaft by a motion of said robot or similar apparatus into contact with asuitably disposed surface, and moving said shank shaft of the robot orsimilar apparatus along said surface in contact with said surface suchthat the friction between said part of said shank shaft and said surfacecauses the rotation of said shank shaft.
 4. A method as set forth inclaim 1, wherein said indexing of said shank shaft comprises:rotatingsaid shank shaft with a low torque; detecting the angular position ofsaid shank shaft by an indicating means provided in said shaft and adetecting means cooperating with said indicating means and providedadjacent to said shank shaft; and stopping the rotation of said shaft ina predetermined angular position and holding said shaft in saidpredetermined position by a stopping and holding force caused by anelectric field or a mechanical brake.
 5. A method for automaticallyremoving a tool from a rotational shank shaft of a robot or similarapparatus performing three dimensional movements, the method comprisingthe steps of:indexing said shank shaft of the robot or similar apparatusto an angular position; disposing a tool tightening member provided inconnection with said indexed shank shaft to a releasing means of saidtool tightening member by a movement of said robot or similar apparatusperforming three dimensional movements, said releasing means beingdisposed at least during said tool removing operation inside themovement range of said robot or similar apparatus; releasing saidtightening member with the aid of said releasing means for releasingsaid tool; and removing said released tool from said shank shaft of therobot or similar apparatus by a movement of said robot or similarapparatus performing three dimensional movements.
 6. A method forremoving a tool as set forth in claim 5, wherein said releasing of saidtool tightening member is performed in two stages in which:a clampingforce provided by said tightening member is removed by a movement ofsaid robot or similar apparatus and a cooperating fixedly mountedopening device, whereafter said tightening member with no clamping forceleft is further opened by a rotatable releasing device such that a partof the tightening member still retaining said tool in its place isrotated or swung open by said releasing device.
 7. A method as set forthin claim 5, wherein said indexing of said shank shaft comprises:movingan indexing means towards said shaft to a predetermined distance fromsaid shaft; rotating said shank shaft with a low torque and such thatsaid indexing means reaches a counterpart thereof provided in said shankshaft, whereby the rotation of said shank shaft stops and the angularposition of said shank shaft is maintained by a cooperation of saidindexing means and said counterpart thereof.
 8. A method as set forth inclaim 7, wherein the rotation of said shank shaft during the indexing isprovided by:moving a part of said shank shaft by a motion of said robotor similar apparatus into contact with a suitably disposed surface, andmoving said shank shaft of the robot or similar apparatus along saidsurface in contact with said surface such that the friction between saidpart of said shank shaft and said surface causes the rotation of saidshank shaft.
 9. A method as set forth in claim 5, wherein said indexingof said shank shaft comprises:rotating said shank shaft with a lowtorque; detecting the angular position of said shank shaft by anindicating means provided in said shaft and a detecting meanscooperating with said indicating means and provided adjacent to saidshank shaft; and stopping the rotation of said shaft in a predeterminedangular position and holding said shaft in said predetermined positionby a stopping and holding force caused by an electric field or amechanical brake.
 10. An apparatus for an automatic tool change of atool (26) disposed in a rotative shank shaft (22) of a robot or similarapparatus capable of performing three-dimensional movements, saidapparatus comprising a tool holder (24) provided in said shank shaft forreceiving said tool, a tightening member (28) for clamping said tool insaid tool holder, tightening and/or releasing means (30,32) of saidtightening member (28), characterized by said apparatus furthercomprisingindexing means (40) for the indexing of the rotationalposition of said shaft (22) of the robot or similar apparatus, and inthat said robot (10) or similar apparatus capable of performingthree-dimensional movements is arranged to move said tightening member(28) of said tool (26) in the indexed shank shaft of the robot orsimilar apparatus to said tightening and/or releasing means (30,32),which means are placed inside a movement range of said robot (10) orsimilar apparatus at least during said tool change operation.
 11. Anapparatus as set forth in claim 10, wherein said means for releasingsaid tightening member (28) comprise a fixedly mounted means (31)arranged to cooperate with the movements of said robot (10) or similarapparatus for removing the clamping force provided by said tighteningmember (28), and a rotatable means (30) for further opening of theremaining non-clamping portion of said tightening member.
 12. Anapparatus as set forth in claim 10, wherein said tightening member is ascrew (28), the rotation of which is arranged to provide a clamping holdon said tool (26).
 13. An apparatus as set forth in claim 10, whereinsaid tightening member is a hydraulically or pneumatically operatedmember, which is arranged to provide a clamping hold from said tool (26)and which is arranged to be connected with a quick-release adapter (36)and a counterpart (37) thereof or in a similar manner to an externalsource of fluid so as to vary a fluid pressure inside said tighteningmember.
 14. An apparatus as set forth in claim 10, wherein said indexingmeans (40) comprise a protruding means (42;49) movable at least in theradial direction of said shaft and disposed adjacent to said shaft andat least one groove, slot, boss or the like receiving means inconnection with said shaft and arranged to receive said protrudingmeans, whereby said protruding means and said at least one groove, slot,boss or the like are arranged cooperatively to stop said rotatable shaft(22) in one or more predetermined angular position(s).
 15. An apparatusas set forth in claim 14, wherein said receiving means comprises atleast one discontinuous groove (44) extending around said shaft (22),said groove including at least one discontinuity (45) arrangedcooperatively with said protruding means (42) to stop the rotation ofsaid shaft.
 16. An apparatus as set forth in claim 14, wherein saidreceiving means comprises at least one sleeve (46) assemblednon-rotatably to said shaft and having at least one boss or projection(47,47') being arranged cooperatively with said protruding means (42) tostop the rotation of said shaft.
 17. An apparatus as set forth in claim10, wherein said receiving means comprises at least one hole or boringor a slot (48) extending in the longitudinal direction of said shaft,said means being arranged cooperatively with said protruding means whichis movable towards and away from said shaft and preferably comprises apin (49) biased with a spring or pneumatic pressure, to stop therotation of said shaft.
 18. An apparatus as set forth in claim 10,wherein said indexing means comprise an indicator (52) disposed on saidshaft (22) and a detector (53) connected cooperatively with saidindicator for detecting the angular position of said shaft, and brakingmeans (54,55) operationally connected with said detector (53) andindicator (52), said braking means being operated electrically,mechanically or by any other suitable means to stop and hold said shaftin a predetermined position.